Yellow fever

Yellow fever

What is yellow fever?

Yellow fever is an infectious viral disease transmitted by mosquitoes in tropical and sub-tropical climates. It is a serious health concern, particularly in sub-Saharan African and some South American countries.

An estimated 200,000 people contract yellow fever each year, the vast majority of them in Africa. Around 30,000 die annually as a result.[1][2]

Causes

Yellow fever is caused by a virus that mainly infects monkeys. However, mosquitoes can transmit the virus from an infected monkey to a human. The virus is not able to be spread directly from person to person.

When the virus enters a person's bloodstream from a mosquito bite, it is able to spread to multiple organs in the body. It is still not clear how the virus causes the characteristic bleeding observed in the toxic stage of the illness.

Remission stage

After about two days with symptoms, most people fight off the infection. However, in about 15-25% of people, the illness goes into remission. This is where the symptoms subside, but the virus is not completely removed from the body. Remission can last between a few hours to a whole day, before they reappear in a more serious form, known as toxic or intoxication stage.[3]

Toxic stage

At this stage, bleeding can occur from multiple internal organs, including the heart, kidneys, spleen, liver and stomach. Symptoms can include:

Coma

A state of deep and prolonged unconsciousness.

Delirium

A mental state caused by temporary disturbances in brain function and characterised by a host of symptoms that may include fluctuating confusion, restlessness, excitement, incoherence, illusions, anxiety, and attention deficit.

Jaundice

A yellowing of the skin, the whites of the eyes and the mucous membranes, due to an accumulation of bilirubin in the blood. Often a symptom of liver problems.

Remission

A partial or complete reversal of the course of illness, such as cancer or a chronic disease. Remission can be spontaneous or the result of therapy.

Seizures

A sudden, involuntary contraction of muscle groups caused by abnormal electrical activity in the brain.

Spleen

An organ in the abdominal cavity that is involved in filtering out old blood cells and fighting infection.

Methods for diagnosis

If a yellow fever infection is suspected, your doctor may perform specific blood tests to identify the presence of the virus or antibodies to the virus. Other blood tests may be performed to assess your liver and kidney function.

Types of treatment

There is no specific treatment for yellow fever. Antibiotics and existing antiviral medications have no effect on the virus. If you are suffering from yellow fever, treatment will focus on managing your symptoms and hydration.

Treatment measures can include:

Rest;

Drinking plenty of fluids - in severe cases, intravenous fluids may be required;

Medication to relieve pain and fever, and;

For people suffering severe kidney damage, kidney dialysis may be recommended.

Dialysis

A mechanical blood-filtering treatment that mimics the function of your kidneys, which normally work as your body’s natural filtration system to remove the body's waste products from the blood.

Prevention

Vaccination

An effective yellow fever vaccine is available and is routinely given to people living in, or travelling to, areas where the virus is commonly found. Some countries require a certificate of vaccination against yellow fever before entering them. The vaccine is given as a single injection and is thought to give decades of protection to the disease.

A vaccination is an effective way of protecting yourself against yellow fever.

Bite prevention methods

A good way of reducing the chance of developing yellow fever is to avoid mosquito bites. In areas where the yellow fever virus is commonly found, you can protect yourself by taking the following measures:

The Aedes aegypti mosquitoes, which is mainly responsible for transmitting yellow fever, are mostly active during the day. Therefore, bed nets and other night-time bite prevention strategies are less useful against yellow fever than for other mosquito-borne diseases such as malaria.

Mosquito control methods

An effective way of controlling Aedes aegypti mosquito numbers is to prevent their access to standing water in which they lay eggs. This requires governments and citizens to be aware of sources of standing water in their environment (containers, puddles, old tyres, pots, etc.) and to empty or seal them.

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